The increasing importance of lasers for surgical applications has resulted in new research into the interaction between laser radiation and tissue. From this research has come an understanding of the requirements for surgical lasers which maximize the ablation of tissue and minimize damage to surrounding areas. A pulsed laser operating at a wavelength of 2.9 micrometers has these characteristics and in addition can be readily transmitted through thin, flexible fluoride-glass fibers, a great advantage for convenience and also for the development of entirely new surgical procedures. The efforts in this proposal would result in the initial development and construction of a pulsed, 2.9-micrometer-wavelength, solid state laser based on erbium-ion-doped crystals. A series of tissue-interaction experiments would be performed with the laser at the Wellman Laboratories of the Massachusetts General Hospital and an overall assessment of the potential of the laser system for further development and commercial application would be carried out. Based on current understanding it appears that the availability of a reliable, pulsed 2.9-micrometer laser would have a significant impact on laser-surgery techniques and capabilities.